<html>
<head>
    <script type="text/javascript">
        function getCookie(c_name) //获取cookie
        {
            if (document.cookie.length>0) {
                c_start=document.cookie.indexOf(c_name + "=");
                {
                    c_start=c_start + c_name.length+1;
                    c_end=document.cookie.indexOf(";",c_start);
                    if (c_end==-1) c_end=document.cookie.length;
                    return unescape(document.cookie.substring(c_start,c_end));
                }
            }
            return "";
        }

        function setCookie(c_name,value,expiredays)//设置cookie
        {
            var exdate=new Date();
            exdate.setDate(exdate.getDate()+expiredays);
            document.cookie=c_name+ "=" +escape(value)+
                ((expiredays==null) ? "" : ";expires="+exdate.toGMTString());
        }

        function checkCookie() //检查cookie
        {
            username=getCookie('username');
            if (username!=null && username!=""){
                // alert(document.cookie);
                alert('Welcome again '+username+'!');
            }
            else {
                username=prompt('Please enter your name:',"");
                if (username!=null && username!=""){
                    setCookie('username',username,90);
                }
            }
        }
    </script>
</head>

<body onLoad="checkCookie()">

</body>
</html>